Hum in speakers gradually increases

Stick · Post by **Stick** » Sat Dec 16, 2006 3:34 am

So, I'm working in my new room, and my Genelecs are producing some 60 cycle hum. The weird thing is that if I shut them off and then turn them back on, the hum is gone (well, way less) and stays that way for awhile. Then at some point later (an hour? two?) I realize the hum is back.

I'm assuming it's some sort of power issue. But I'm pretty clueless. We set up the electrical with a sub panel in the studio, and added a ground pole to the whole system (there wasn't one prior). I've got pretty much the whole studio running from a Furman conditioner (PL-PLUS). Though to test it, I plugged one of the Genelecs directly into the wall (bypassing the Furman), and it does the same thing.

Thoughts?

Post by **Aaronw** » Sat Dec 16, 2006 8:29 am

Does the hum come and go? Maybe when a fridge is running or HVAC unit is running?

Is the input to the Genelec's balanced or unbalanced?

Is your source (console or ??) balanced and grounded?

Is the console/source on a different phase or leg than the monitors?

Post by **Aaronw** » Sat Dec 16, 2006 8:32 am

I just took another look at the room.

Are those halogens in the ceiling? Are they on a dimmer switch?

Stick · Post by **Stick** » Sat Dec 16, 2006 8:56 am

Hey Aaron,

Everything's balanced.

Yes halogens, but no dimmers.

It doesn't come and go once the hum has built up, it stays constant. Constantly annoying.

The source is a StudioComm 50/51 set up. It's balanced, and it's on the same Furman as the rest of the studio. Side note... the Studiocomm's rack piece where all the cables connect has been making a similar hum. But it's actually coming from the rack itself. But, if I pull the plug on the StudioComm, that hum quits, but the speakers still hum (assuming they're already humming).

Post by **Aaronw** » Sat Dec 16, 2006 9:02 am

Do they still hum w/ the input cables unplugged from them? Let's narrow it down to power or ground loops or issue's w/ monitors.

Stick · Post by **Stick** » Sat Dec 16, 2006 9:12 am

Still hums with the cable disconnected. So, power or something's up with the monitors.

Post by **Aaronw** » Tue Dec 19, 2006 2:27 am

Have someone start flipping breakers to everything in the house while you're listening and see if the noise goes away, get's quieter or...

TomVan · Post by **TomVan** » Wed Dec 20, 2006 7:39 am

Just a thought here.
Your speakers are not sheilded like computer speakers are.
That big beautiful LCD or Plasma above the speakers might be creating your hum. Especially if you see a warble in the screen closest to the speaker.
The only problem I ever had with hum was an ac/dc power converter for my DI. All I had to do was move them away from the rest of the gear and it solved the prolem
And that easy move took a few months to find.
Good luck
Tom